This invention relates to an elastic suspension arrangement for an electric fuel pump and/or a fuel filter and/or an accumulator that are part of the fuel system of motor vehicles. Particularly preferred embodiments relate to such suspension arrangements for passenger cars equipped with a mixture-compressing internal-combustion engine. Such elastic suspension arrangements have been contemplated which included portions which are rubber-elastic between the part being suspended and the suspension member.
In previously contemplated arrangements, the fuel pump, the fuel filter and the accumulator are firmly combined with one another to form an oblong constructional unit. At this constructional unit, at its ends that are opposite one another, one rubber - metal element respectively is fastened by means of which it can swingably be fastened on holding means provided at the bottom side of the underbody of a vehicle. By means of the rubber - metal elements it is to be ensured that the constructional unit, because of the fuel pump that is designed as a roller vane pump and therefore pulsates heavily, is disconnected from the underbody with respect to vibrations in order not to let pulsation noises and mechanically created noises of the pump reach the interior of the vehicle as structure-borne noise, where, because of their high frequency they would be found to be unpleasant.
The disconnection or uncoupling of vibrations carried out by means of the rubber metal elements has proven to be unsatisfactory because the natural frequency of the constructional unit was too close to the exiting frequency of the fuel pump. The cause in this case is the fact that the rubber - metal elements consist of a rubber-elastic connecting member and a metal plate vulcanized to it having threaded bolts as the suspension members.
Because of a required good adhesive connection between the connecting member consisting of rubber and the metal plate, the shore hardness of the rubber, however, can only be reduced to a certain value, or the elasticity rate can only be reduced insufficiently. In addition, the rubber - metal connection, in the case of rubber - metal elements, was often made incorrectly which frequently results in the replacement of such a suspension device.
Finally, during the mounting of the constructuional unit, installation difficulties occur frequently, caused by the tolerances in the mutual assignment of the threaded bores on the vehicle body to the anchoring of the threaded bolts of the metal plates. Thus the elastic connecting members of the rubber - metal elements are pulled, upset or twisted within themselves causing a hardening of the rubber mass of the connecting members.
This invention is based on the objective of providing a suspension device of the above-described general type by means of which an effective vibratory disconnection can be achieved between the fuel pump and/or the accumulator and the underbody of the motor vehicle. In preferred embodiments, the suspension device should be easy to manufacture and, irrespective of existing manufacturing tolerances between the fastening points on the vehicle body, should be easy to mount. Also, on the parts to be suspended, holding means to be provided for the purpose of their suspension at the connecting member should not be necessary.
These objectives are achieved according to the invention by providing that the connecting member includes rubber-elastic material with an opening therethrough accommodating a prestress fit over a housing of the part being suspended. In especially preferred embodiments the connecting member consists of the rubber-elastic material.
In the case of the construction according to the invention, the connecting element and the suspension member of the suspension device form two constructional parts that are first separate from one another, the suspension member of which must be fastened separately at the underbody of the vehicle. The connecting element, for the swingable suspension of one or several parts of the fuel system, must only be fitted on the housing of the part and fastened at the suspension member. In preferred embodiments the suspension member is connected to the rubber-elastic connecting element by hooking into the same.
The suspension according to the invention also ensures increased safety in the area of the suspension in the case of an accident where a deformation of the body occurs because the at least one elastically suspended part of the fuel system, because of the soft formation of the connecting element, can yield to deforming parts of the vehicle body.
Synthetic and natural polymers having a rubber-elastic behavior (synthetics or caoutchouc) and rubber are suitable for making the connecting member. In certain preferred embodiments of the invention the opening walls of the rubber-elastic connecting member closely surround the whole circumference of the housing of the fuel system part being suspended. In this case, it is advantageous to further develop the connecting element according to preferred embodiments of the invention by providing that the same has a low spring rate and/or includes a slot shaped recess to thereby improve the elastic soft support of the part being suspended.
The low rate of elasticity or the soft formation of the connecting element result in a strong yielding and thus in the endeavored good disconnection or isolatio of vibrations, in which case its elasticity also makes possible an advantageous adaptation to a production-caused offset of the suspension member at the underbody of the vehicle.
In especially preferred embodiments, the low rate of elasticity of the connecting element can only be achieved by the fact that the development of the suspension member and of the connecting element can be separated from one another, making a vulcanized connection superfluous. This makes it possible to select the softness of the rubber-elastic material for the connecting element to be very high.
The fastening of the connecting element at the suspension member is advantageously achieved according to certain preferred embodiments by providing the connecting element with a slot shaped recess which is fitted on a hook shaped part of the suspension member.
The swingable suspension of the fuel pump or the other parts belonging to the fuel system at the underbody of the vehicle can be carried in the latter case, it is advantageous to develop the connecting elements as disk or donut shaped rubber-elastic elements which surround the housing part being supported at spaced apart locations. Preferably a single suspension member with opposite facing anchoring parts engage in recesses of the respective rubber elastic elements.